NEW YORK, May 4 (Reuters) - Goldman Sachs Group Inc’s (GS.N) market-making unit has been censured and fined $450,000 after U.S. regulators found hundreds of violations over how it processed customer trades involving short sales of stocks.

The U.S. Securities and Exchange Commission and NYSE Regulation said Goldman Sachs Execution & Clearing LLP violated emergency requirements adopted in September 2008, two days after Lehman Brothers Holdings Inc LEHMQ.PK went bankrupt, to limit naked short selling.

A short sale occurs when a customer borrows a security, sells it in a bet the price will go down, and then buys it back later to replenish the lender. A naked short sale occurs when the customer has no intention to borrow the security.

Half the penalty will go to NYSE Regulation, a unit of NYSE Euronext NYX.N, and the rest to the federal government. Goldman agreed to settle without admitting wrongdoing.

The fine was announced Tuesday, less than three weeks after the SEC filed a civil fraud lawsuit against Goldman in an unrelated case.

Regulators said that because of a bookkeeping error, the Goldman unit between Dec. 9, 2008, and Jan. 22, 2009, accepted about 385 orders to short stocks where it had not first borrowed or arranged to borrow the securities as collateral.

They also said the Goldman unit failed about 68 times over that period to timely close out market-making positions in stocks or notify customers about such lapses.

According to the SEC, the unit’s procedures were “inadequate in that they relied too heavily on individuals to perform manual tasks and calculations, without sufficient oversight or verification of accuracy.”

NYSE Regulation also found supervisory violations at the Goldman unit from Sept. 24, 2008, to Jan. 22, 2009.

A Goldman spokesman said the violations resulted from a processing error, and had no financial effect on clients. He also said the unit clears about 3 million trades a day, and has improved its automated processes. (Reporting by Jonathan Stempel; Additional reporting by Dan Wilchins; Editing by Tim Dobbyn and Maureen Bavdek)